Hot air heated shrinking tunnel



Oct. 6, 1970 H. BECK 3,531,873

HOT AIR HEATED SHRINKING TUNNEL Filed July 22, 1968 Fig. 1

37 37 M /f \/4 /f l l L 16 ff-15 78 20 73 t f7 4 77 Z V 19 27 UnitedStates Patent O 3,531,873 HOT AIR HEATED SHRINKING TUNNEL Hans Beck,Urbanstrasse 27, Nurtingeu Wurttemberg, Germany Filed July 22, 1968,Ser. No. 746,357 Claims priority, application Germany, July 21, 1967,1,561,983 Int. Cl. F26b 19/00 U.S. Cl. 34-223 7 Claims ABSTRACT 0F THEDISCLSURE A hot-air circulating system for a tunnel for heat shrinkingplastic foil packaging materials comprises two blower systems forcirculating air in closed circular paths, each path being disposed inplanes perpendicular to each other, with some of the air in one pathbeing commingled with the air in the other path.

The invention concerns a hot-air heated shrinking tunnel for goodspacked in shrinkable plastic foil, with a conveyer belt for the goodspassing through the tunnel in longitudinal direction, with at least onehot-air blower each arranged at the ceiling and floor of the tunnel, forproduction of circular currents of hot air closed within themselves anddirected into the tunnel.

It has been known (German Utility Pat. 1,893,045) to use two hot airblowers in the case of a hot air heated shrinkage tunnel of the kindmentioned, which introduces circular currents of hot air, directed inparallel to one another, from above or below into spaces of the tunnel.This guidance of the currents of hot air has the disadvantage that theentire cross sectional width of the tunnel will be fed owing hot aironly in an incomplete manner, so that this will result, especially inthe case of relatively wide articles that have to be packed, inimperfectly shrunk packaging foils which have not been drawn tightlyaround the articles.

An object of this invention is to overcome this disadvantage justdescribed and of proposing an arrangement with the help of which theinside space of a hot-air heated shrinking tunnel can be filledcompletely with owing hot air, so that considerably better qualitypackaging can be achieved.

According to the invention this task is solved through the fact that thedirection of flow of one current of hot air will run in parallel to thelongitudinal section of the tunnel and that of the other current of hotair will run transversely in relation to this plane, in such a mannerthat both currents of hot air commingle with each other, at leastpartially.

In case of a preferred design of the invention, a tunnel hood isarranged above the iioor of the tunnel and, in order to change theeffective cross section of the tunnel, the hood, in relation to thefloor, can be adjusted in height, whereby the lateral walls of the hoodencircle the oor at the sides thereof in telescoping fashion. In thecase of this design of the invention, the additional advantage will beachieved that the inside cross section of the tunnel can be adapated tothe height of the goods that are to be wrapped, which makes possible afurther improved quality of the packaging with a saving of heat energyin combination with the currents of hot air introduced in accordancewith the invention.

The following description of a preferred design of the invention servesin connection with the attached drawing for further clarication.

FIG. 1 shows a longitudinal section of a shrinkage tunnel in accordancewith a preferred form of the invention;

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FIG. 2 shows a cross section of the tunnel along the line 2-2 in FIG. 1and FIG. 3 shows a front view of the tunnel as viewed from the left inFIG. 1.

A tunnel oor 2 is mounted tixedly on a supporting frame 1, which oor iscovered by a tunnel hood indicated generally numeral 3. In thelongitudinal direction of the tunnel, formed by the Hoor 2 and the hood3, there is a conveyer belt 4, which is permeable to air throughout,which can consist, for example, of an endless conveyer belt which ispreferably perforated, guided over rollers 5 and driven in conventionalmanner which has not been shown in the drawing in detail. On theair-permeable conveyer belt, the goods wrapped into shrinkable Plasticfoil are transported through the shrinking tunnel.

The oor of the tunnel and the ceiling 6 of the tunnel, formed by thehorizontal part of the hood 3, are provided With recesses 7 and 8, ineach of which an impeller of a hot air blower 9 and 10, as well aselectrically heating elements 11 and 12 have been arranged. The recesses7 and 8, whose shapes can be recognized in FIGS. 1 and 2, form guidewaysfor the currents of hot air produced by the blowers 9 and 10. Thelongitudinal axis of recess 7 in the floor 2 of the tunnel runs inparallel to the longitudinal axis of the tunnel. On the other hand, thelongitudinal axis of recess 8 in the ceiling 6 of the tunnel runstransversely in relation to the longitudinal axis of the tunnel. As aresult, the direction of ow of the currents of hot air produced by theblower 9 will ow in a circular path, indicated by arrow 13, disposed inparallel to the piane of the longitudinal section of the tunnel, whilethe direction of flow of the currents 14 of hot air, likewise closed inan circular path and produced by `blower 10, is directed perpendicularlyin relation to the plane of the longitudinal section of said tunnel.Both currents 13, respectively, and 14, respectively, commingle witheach other about in the middle of the tunnel, a fact which has not beenespecially shown in the drawing. The current 13 of hot air produced byblower 9 lls the tunnel essentially in a longitudinal direction with hotair, while blower 10, on the basis of its cross directed current 14,ensures that the entire cross section of the tunnel is lled with hotair. ln the drawing only one blower has been shown arranged on the door2 of the tunnel or on the ceiling 6 of the tunnel, but it isself-evident that if required it is also possible to arrange several hotair blowers one behind or one beside another on the tloor and on theceiling.

As shown, the tunnel hood 3 has an approximately U- shaped cross sectionand it encompasses with its lateral walls 15 and 16 the side Walls 17and 18 standing upwardly in a telescoping way from floor 2. In thismanner it is possible through lifting or lowering the hood 3 of thetunnel to change the effective cross section of the tunnel and to adaptit in correspondence with the cross sectional shape of a material thatis to be packaged, which is of a considerable advantage for the sake ofa quick shrinkage and for the saving of heat energy.

As can be seen in the figures, the hood 3 of the tunnel has beenattached by its lateral walls 15 and 16 to columns 19 and 20, which inturn rest on horizontally disposed supports 21 and 22. A screw spindledrive engages with supports 21 and 22, in order to lift or lower hood 3of the tunnel.

In the case of the drive, sketched in the drawing, a nut 24 shifts on ascrew spindle 2S upon turning of a crank 23. The nut 24 is connectedpivotally with a guide element 26, which is slidably seated on an arm ofa toggle lever 28 mounted xedly on a shaft 27. The other arm of thistoggle lever 28 has been connected pivotally with support 21. Thesupports 21 and 22 are furthermore sup- 3 ported by levers 29 mountedfor rotational movement, one of which likewise is xedly attached onshaft 27 and is moved with lever 28.

In the operation of crank 23, the toggle lever 28 shifts and carriesalong the supports 21 and 22 either upward or downward, depending on thedirection of rotation of the crank, as a result of which the hood 3covering the tunnel is moved up or down with columns 19 and 20, whichare supported slidably on the supports 2l and 22.

It is self-evident that the change in the cross section of the tunneldescribed heretofore, through the up and down movement of the hoodcovering the tunnel, can be used not only in the case of a shrinkingtunnel heated by means of hot air blowers but that it can be heated justas well in some different manner, for example, by means of electricheating coils.

It will also be observed from FIGS. 1 and 2 that guide varies 31 havebeen arranged inside the tunnel, which can be angularly rotationallyadjusted preferably from outside the hood and which serve for thepurpose of adjusting the currents of hot air correspondingly and independence on the shape of the material that is to be packaged.

On both front sides of the shrinking tunnel, according to the invention,individually adjustable plates 32 have been arranged by means of whichthe size of the inlet and outlet openings can be adjusted to the shapeof the material 33 that is to be packaged (see FIG. 3). In case of thedesign as shown, these adjustable plates 32 consist of individualsheetmetal plates with longitudinal holes 34- on which the plates areheld by means of adjusting screws 35 at the front sides of the hood 3.

l claim:

1. Hot-air heated shrinking tunnel for materials packed in shrinkableplastic foil with a horizontal conveyor belt for the goods passingthrough in a longitudinal direction of the tunnel and having at leastone hot air blower arranged at the ceiling and another hot-air blower onthe Hoor of the tunnel for producing two respective circular closedcurrents of hot air directed into the tunnel, each of the respectiveblowers having an inlet means and at least two horizontally spacedoutlet means arranged respectively on opposite sides of the inlet meansto direct a current of air toward the conveyor belt, characterized inthat the direction of ow of one current of hot air runs in parallel tothe vertical plane of the longitudinal section of the tunnel and that ofthe other current of hot air runs perpendicularly in relation to thisplane, in such a manner that one respective current of hot aircommingles with the other respective current of hot air at leastpartially.

2. Shrinking tunnel according to claim l, characterized in that for thecontrol of the circular currents of hot air, adjustable sheetmetalguides have been provided in the tunnel.

3. Shrinking tunnel according to claim 1, characterized in that at theinlet and outlet openings of the tunnel, individually adjustable plates(32) are mounted by means of which the size of the openings at the endsof the tunnel can be adapted to the shape of the goods which are to bepackaged.

4. Shrinking tunnel according to claim 3, characterized in that theplates are provided with longitudinal holes for attachment by means ofadjusting screws at the ends of the tunnel.

5. Shrinking tunnel according to claim 1, characterized in that thetunnel is formed by a hood arranged above the Hoor of said tunnel, whichhood can be adjusted with regard to height as compared to the Hoor for achange in the effective cross section of the tunnel, and wherein theside walls of the hood engage with the oor laterally in telescopingfashion.

6. Shrinking tunnel according to claim 5, characterized in that meansfor the adjustment in height of the hood comprises a lever bar withscrew spindle drive.

7. Shrinking tunnel according to claim 5, characterized in that thefloor of the tunnel is provided with side walls which are arranged fortelescoping engagement with the inner sides of the side walls of thehood.

References Cited UNITED STATES PATENTS 1,941,560 l/1934` Lee 34-2422,295,475 9/1942` Hurxthal 34-216 XR 3,389,478 6/1968 Cline 34-2l6FREDERICK L. MATTESON, JR., Primary Examiner H. B. RAMEY, AssistantExaminer U.S. Cl. X.R. 34-236; 53-184

